Brian Tillman wrote:
Anett wrote:

Sorry for my indistinct description. The NDR is, off course, sent back
to the original sender.

That's what I thought. Is the NDR generated by your mail server or one
outside of your system? If the latter, you have no hope of addressing the
issue.
--
Brian Tillman

The NDR is created by our back-end server and sent out.

Anett